StreamAlert utilizes Kinesis Streams, which can “continuously capture and store terabytes of data per hour from hundreds of thousands of sources” [1]

What’s the maintenance/operational overhead?

Limited; StreamAlert utilizes Terraform, Kinesis Streams and AWS Lambda, which means you don’t have to manually provision, manage, patch or harden any servers

Does StreamAlert support analytics, metrics or time series use-cases?

StreamAlert itself does not support analytics, metrics or time series use-cases. StreamAlert can send data to such tools or you can use one of many great open source and commercial offerings in this space, including but not limited to Prometheus, DataDog and NewRelic.

Is StreamAlert intended for synchronous (blocking) or asynchronous decision making?